System and method of use for revascularizing stenotic bypass grafts and other occluded blood vessels

ABSTRACT

A system and method for opening a lumen in an occluded blood vessel, e.g., a coronary bypass graft, of a living being. The system comprises an atherectomy catheter having a working head, e.g., a rotary impacting impeller, and a debris extraction sub-system. The atherectomy catheter is located within a guide catheter. The working head is arranged to operate on, e.g., impact, the occlusive material in the occluded vessel to open a lumen therein, whereupon some debris may be produced. The debris extraction sub-system introduces an infusate liquid at a first flow rate adjacent the working head and withdraws that liquid and some blood at a second and higher flow rate, through the guide catheter to create a differential flow adjacent the working head, whereupon the debris is withdrawn in the infusate liquid and blood for collection outside the being&#39;s body. The introduction of the infusate liquid may also be used to establish an unbalanced flow adjacent the working head to enable the atherectomy catheter to be steered hydrodynamically. A guide wire having an inflatable balloon on its distal end may be used with the atherectomy catheter to block the flow of debris distally, while enabling distal tissues to be perfused with an oxygenating liquid. At least one flow control port may be provided in the guide catheter to prevent collapse of the vessel being revascularized. A cradle is provided to fix the guide catheter and guide wire in position within the body of the being while enabling the atherectomy catheter to be advanced along the guide wire and through the guide catheter. The guide catheter includes a wear resistant coating and is constructed so that its distal end includes plural sections of different outside diameters, with the distal most section being of the smallest outside diameter. A control console is provided to establish various modes of operation of the system based on manual inputs via switches or voice commands via voice recognition circuitry. A video panel displays the various modes of operation and instructions to the operator.

RELATED APPLICATIONS

This application is a Continuation-In-Part of U.S. patent applicationSer. No. 09/594,131, filed on Jun. 14, 2000, entitled System and Methodof Use for Revascularizing Stenotic Bypass Grafts and Other OccludedBlood Vessels, which is a Continuation of U.S. patent application Ser.No. 09/233,712, filed on Jan. 19, 1999, entitled Improved System AndMethod Of Use For Revascularizing Stenotic Bypass Grafts And OtherOccluded Blood Vessels, now U.S. Pat. No. 6,080,170, which in turn is aContinuation-In-Part of U.S. patent application Ser. No. 08/900,598,filed on Jul. 25, 1997, entitled System And Method Of Use ForRevascularizing Stenotic Bypass Grafts And Other Blood Vessels, now U.S.Pat. No. 5,879,361, which in turn is a Continuation-In-Part of U.S.application Ser. No. 08/690,438, filed on Jul. 26, 1996, entitled SystemAnd Method Of Use For Revascularizing Stenotic Bypass Grafts And OtherBlood Vessels, now U.S. Pat. No. 5,779,721, all of which are assigned tothe same assignee as this invention, and whose disclosures areincorporated by reference herein.

BACKGROUND OF THE INVENTION

This application relates generally to medical instruments and methods ofuse to remove occlusive material from a vessel, duct or lumen within thebody of a living being.

Catheter instruments have been suggested or disclosed in the patentliterature for effecting non-invasive or minimally invasiverevascularization of occluded arteries. For example, in U.S. Pat. No.4,445,509 there is disclosed a recanalization catheter designedspecifically for cutting away hard, abnormal deposits, such asatherosclerotic plaque, from the inside of an artery, while supposedlypreserving the soft arterial tissue. That recanalizing catheter includesa sharp-edged, multi-fluted, rotating cutting tip mounted at the distalend of the catheter and arranged to be rotated by a flexible drive shaftextending down the center of the catheter. The rotation of the cuttinghead is stated as producing a “differential cutting” effect, whereuponrelatively hard deposits are cut away from relatively soft tissue.Suction ports are provided to pull the hard particles produced by thecutting action into the catheter for removal at the proximal end thereofso that such particles do not flow distally of the catheter where theycould have an adverse effect on the patients' body.

In U.S. Pat. No. 4,700,705, which is assigned to the same assignee asthis invention and whose disclosure is incorporated by reference herein,there are disclosed and claimed catheters and methods of use foreffecting the opening of a vessel, duct or lumen, such as the opening ofa atherosclerotic restriction (partial or total occlusion) in an artery.These catheters are elongated flexible members of sufficient flexibilityto enable them to be readily passed through the body of the patient tothe situs of the atherosclerotic plaque in the artery to be opened. Aworking head is mounted at the distal end of the catheter and isarranged for high-speed rotation about the longitudinal axis of thecatheter. In some embodiments the catheter may eject fluid at theworking head to expedite the restriction-opening procedure.

In U.S. Pat. No. 4,747,821, which is also assigned to the same assigneeas this invention and whose disclosure is incorporated by referenceherein, there is disclosed and claimed other catheters particularlysuited for revascularization of arteries. Each of those cathetersincludes a rotary working head having at least one non-sharp impactingsurface to effect material removal without cutting. Moreover, thosecatheters are arranged to eject fluid adjacent the working head toexpedite the revascularization procedure. In particular, the rotation ofthe working head produces a powerful, toroidal shaped vortex contiguouswith the working head which has the effect of recirculating anyparticles that may have been broken off from the material forming thearterial restriction so that the working head repeatedly impacts thoseparticles to reduce their size.

In U.S. Pat. No. 5,042,984, which is also assigned to the same assigneeas this invention and whose disclosure is incorporated by referenceherein, there are disclosed and claimed catheters whose working headsinclude impacting surfaces of differing aggressiveness which may beselectively brought into engagement with the restriction to be opened.Such catheters also make use of exiting jets of liquid as describedabove.

Other atherectomy devices for enlarging an opening in a blood vesselhave been disclosed and claimed in the following United States patents:U.S. Pat. No. 4,589,412 (which is assigned to the same assignee as thisinvention and whose disclosure is incorporated by reference herein);U.S. Pat. Nos. 4,631,052; 4,686,982 (which is assign ed to the sameassignee as this invention and whose disclosure is incorporated byreference herein); U.S. Pat. No. 4,749,376 (which is assigned to thesame assignee as this invention and whose disclosure is incorporated byreference herein); U.S. Pat. Nos. 4,790,813; 5,009,659; 5,074,841;5,282,484; 5,366,463; 5,368,603; 5,402,790; 5,423,742; and 5,429,136.

Some rotary atherectomy devices are in use in this country forrevascularizing occluded arteries. However, their use is limited to somevery selected applications. Thus, in many instances a vascular occlusionof a coronary artery can only be treated by coronary bypass surgerywherein a graft, e.g., a saphenous vein section and/or mammary arterysection, is surgically shunted across the occluded coronary artery.Unfortunately a significant percentage of bypass surgical grafts becomere-occluded over time. Thus, the re-occluded graft has to be eitherbypassed by another graft (i.e., second bypass surgery), or there-occluded graft has to be revascularized (i.e., its lumen reopened) bysome intravascular procedure. If the occluded graft is not totallyoccluded, balloon angioplasty may be indicated to reopen the graft.Where, however, the graft is totally occluded or heavily occluded byfrangible deposits balloon angioplasty is.unavailable. Thus, ifrevascularization of such a graft is desired, resort may be to rotaryatherectomy.

One currently available rotary atherectomy device is the ROTOBLATOR®System of Heart Technology, Inc. That system utilizes a catheter havinga diamond coated elliptical burr which is rotated at a high rate ofspeed, e.g., up to 190,000 rpm. The burr serves to break theatherosclerotic plaque into fine particles which are allowed to remainin the patient's body for disposal by the patient's reticuloendothelialsystem.

As is known to those skilled in the art, one problem with a rotaryatherectomy device is that unless the debris produced is so small andbenign that it can be left within the patient's vascular system theremust be some means to ensure that the debris does not flow upstream intothe aorta during the procedure or into the downstream artery graft atthe break-through point when the device comes out the distal side of atotal occlusion, since either action could present a significant hazardto the patient. In particular, the former route risks stroke, the laterroute risks local ischemia of heart muscle when debris blocks off smallarteries.

Thus, the collection and/or aspiration of debris produced during therevascularization of occluded arterial bypass grafts or other bloodvessels is getting considerable attention in the medical arts. Forexample, Possis Medical, Inc., the assignee of U.S. Pat. Nos. 5,370,609and 5,496,267, provides catheter devices designated as the ANGIOJETRapid Thrombolectomy System and the ANGIOJET Rheolytic ThrombolectomySystem. These devices are presumably constructed in accordance withthose patents and are believed to be presently undergoing clinicaltrials. The catheter devices disclosed in those patents utilize highvelocity jets of saline to abrade the blockage. In Particular, thepatents disclose utilizing the momentum of the saline jets to create alocal vacuum to entrain any particulate material produced by therevascularization procedure, with the momentum and the local positivepressure being sufficient to carry the saline and debris to a returncollection bag.

Another atherectomy device which is currently undergoing clinical trialsis the Coronary TEC® System of Interventional Technologies, Inc. Thatdevice is believed to be the subject of U.S. Pat. No. 5,224,945, andbasically comprises a catheter having a working head with microtomesharp blades for cutting plaque circumferentially. The excised plaque isextracted by suction through a central lumen in the catheter into anexteriorly-located vacuum bottle. No control of the quantity of flow ofthe debris-carrying fluid from the catheter is disclosed.

U.S. Pat. No. 5,030,201 (Palestran) discloses a system including anexpandable atherectomy catheter arranged to be rotated to cut through anoccluded artery to revascularize it. The atherectomy catheter includesan expandable cutting head having plural elongated cutting members whichare mounted on a flexible torque tube incorporating a vacuum oraspiration system for retrieval of excised material. The cutting head isarranged to be rotated to cause the elongated members to cut awayatheromatous material or blood clots. The atherectomy catheter isarranged to be inserted into the blood vessel through a coaxial deliverycatheter, also forming a part of the system. The mechanism foraspirating particles of atheromatous material or blood clots removed bythe elongated cutting members is disclosed as being in the form of avacuum port provided at the proximal end of either the deliverycatheter, the atherectomy catheter or a “retracting catheter” which alsoconstitutes a part of the system. Saline solution or some other irrigantis infused through one of the catheters of the device that is not beingused for aspiration. The infusion rate of the saline solution isbalanced with the aspiration rate to avoid any net removal of fluid fromthe vessel. In particular, the patent teaches that by balancing theinfusion rate of the saline solution to the aspiration rate, the netremoval of fluid from the vessel can be brought close to zero, therebyminimizing blood loss.

While the balancing of the infusion and aspiration flow rates tominimize blood loss may be desirable, such action does not insurepositive removal of all debris produced during the revascularizationprocedure.

Accordingly, a need exists for apparatus and a method of use torevascularize partially or totally occluded blood vessels, whilepositively assuring that any particles produced during therevascularization procedure are removed from the patient's body. In thecase of partially or totally occluded coronary bypass grafts, a needexists for intravascular atherectomy apparatus and methods of use foreffectively producing a lumen through the occlusion for the free flow ofblood, without the risk that any debris produced during the lumenopening procedure will enter into the aorta or downstream of theocclusion once it has been crossed or opened.

SUMMARY OF THE INVENTION

A system for opening a lumen in an occluded blood vessel, e.g., acoronary bypass graft, of a living being's vascular system locateddownstream of another blood vessel, e.g., the aorta, from which bloodwill flow to the occluded blood vessel. The system basically comprises aguide catheter, a lumen-opening catheter, a debris blocking member, anda fluid flow system.

The guide, catheter has a distal end portion and at least one bloodentrance port located proximally of the distal end portion. Thelumen-opening catheter extends through the guide catheter to establish afluid flow passageway therebetween and has a working head, e.g., arotatable impacting member, for location immediately adjacent theocclusive material within the occluded blood vessel portion. The workinghead is arranged for operating on the occlusive material, e.g.,repeatedly impacting it, to open a lumen for the freer flow of bloodtherethrough. Some debris may be produced by the operation of theworking head.

The debris blocking member is located distally of the working head toprevent debris from flowing distally thereof.

The fluid flow system is arranged to introduce an infusate liquid at afirst flow rate adjacent the working head and to withdraw that liquidthrough the passageway between the guide catheter and the lumen openingcatheter at a second and higher flow rate to create a differential flowadjacent the working head, whereupon debris produced by the operation ofthe working head is withdrawn by the differential flow and flows withthe liquid proximally through the passageway for extraction.

The blood entrance port in the distal end portion of the guide catheteris in communication with the passageway between the guide catheter andthe lumen opening catheter, whereupon blood from the patent blood vesselportion may enter for merger with the liquid and debris flowing throughthat passageway.

The debris blocking member is an inflatable balloon is provided at thedistal end of the instrument to physically block the egress of anydebris downstream of the apparatus. Perfusion means is preferablyprovided to inflate the balloon and to oxygenate downstream tissue whenthe balloon is inflated.

BRIEF DESCRIPTION OF THE DRAWINGS

Many of the attendant advantages of this invention will readily beappreciated as the same becomes better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings wherein:

FIG. 1 is a schematic diagram, partially in section, of a system of thesubject invention shown during the process of opening a lumen in atotally occluded coronary bypass graft so that blood can flowtherethrough;

FIG. 2 is an enlarged view, partially in section, of a portion of thesystem of FIG. 1 shown during the process of opening a lumen in theoccluded coronary bypass graft;

FIG. 3 is an even more greatly enlarged view, partially in section, of aportion of the system shown in FIG. 2;

FIG. 4 is a reduced isometric view of the portion of the system shown inFIG. 3;

FIG. 5, is an illustration showing the apparatus of FIG. 1, partially insection, during the process of revascularizing a totally occludedfemoral artery downstream of the profunda femoris;

FIGS. 6A and 6B together are an illustration of another embodiment ofthe system of this invention for revascularizing or opening a lumen in acoronary bypass graft;

FIG. 7 is an enlarged isometric illustration of a portion of aninstrument forming a component of the system shown in FIGS. 6A and 6Bduring the process of revascularizing a diseased bypass graft;

FIG. 8 is an enlarged longitudinal sectional view of the distal end ofthe instrument shown in FIG. 7;

FIG. 9A is an isometric view of a portion of another preferredembodiment of this invention making use of a guide catheter having atleast one flow regulation port to ensure that the vessel beingrevascularized does not collapse during the extraction of the debrisproduced by the revascularization;

FIG. 9B is an isometric view of another portion of the embodiment of thesystem shown in FIG. 9;

FIG. 10 is an enlarged isometric view of the distal end of theatherectomy catheter, guide catheter and guide wire of the embodiment ofFIG. 9A shown during revascularization of a coronary bypass graft, wherethe guide catheter tightly fits within the bypass graft;

FIG. 11 is a view similar to FIG. 10 but where the guide catheter fitsloosely within the bypass graft;

FIG. 12 is a greatly enlarged longitudinal sectional view of the distalend of an atherectomy catheter forming a part of the embodiment of thesystem of FIG. 9A;

FIG. 13 is an enlarged longitudinal sectional view of the proximal endof the atherectomy catheter of the system of FIG. 9A;

FIG. 14 is an enlarged longitudinal sectional view similar to FIG. 8,but showing a modified guide wire and distally located balloon for usewith the systems of this invention;

FIG. 15 is a graph showing the four potential sizes and numbers of flowregulation ports for the guide catheter and their potential forprecluding collapse of the vessel being revascularized; and

FIG. 16 is a view similar to that of FIG. 10 but showing a method ofproviding a stent in an occluded blood vessel section, e.g., a bypassgraft, to revascularize it, and with the debris extraction system makinguse of a guide catheter tightly engaging the wall of the blood vesselsection;

FIG. 17 is a view similar to that of FIG. 11 but showing a method ofproviding a stent in an occluded blood vessel section, e.g., a bypassgraft, to revascularize it, and with the debris extraction system makinguse of a guide catheter not engaging the wall of the blood vesselsection;

FIG. 18 is an isometric view of a complete revascularization systemconstructed in accordance with this invention, with portions thereofbeing broken away to show various components of the system; and

FIG. 19 is a plan view of a coated guide wire having a balloon mountedthereon as used in the system of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now in greater detail to the various figures of the drawingswherein like reference characters refer to like parts, there is shown at20 in FIG. 1 a system for revascularizing or opening a lumen through acoronary bypass graft which has become occluded, such as by theformation of a stenotic lesion or the build-up of plaque therein. Asused herein the term “occluded” is given its broadest interpretation.Thus, an “occluded” graft or blood vessel may be either totally blockedor only partially blocked (i.e., there is a passageway or lumen throughwhich some blood may flow).

The system 20 is arranged to be used for forming or enlarging a lumenthrough any blood vessel within the body of a living being, e.g., anoccluded femoral artery downstream of the profunda femoris, notnecessarily an occluded coronary bypass graft or an occluded coronaryartery. In particular, the system 20 is arranged to produce a channel orlumen or to enlarge a lumen through the occlusive material within thevessel and to ensure that any particles of that material which areremoved or broken away, during the revascularization procedure areprevented from flowing into the contiguous vascular system. When thesystem 20 is used for revascularization of occluded coronary bypassgrafts, a primary application for the system 20, the debris produced isdrawn into the system for extracorporeal removal and is thus preventedfrom entering the aorta.

As can be seen in FIG. 1, the system 20 basically comprises an“atherectomy” catheter 22, a guide catheter 24, an introducer sheath 26,a drive sub-system 28, and a debris removal sub-system 30. Theatherectomy catheter 22 is in the form of an elongated flexible tubularbody member or jacket at the free or distal end of which is located arotatable working head 32. The working head 32 is generally similar tothat described in U.S. Pat. No. 4,747,821. Alternatively, the workinghead may be constructed in accordance with the teachings of U.S. Pat.Nos. 4,679,558, 4,686,982, 4,749,376, 5,042,984, and 5,097,849, all ofwhich are also assigned to the same assignee as this invention, andwhose disclosures are also incorporated by reference herein. In fact,the working head may be any device for opening a lumen through theocclusive material.

In use the atherectomy catheter 22 is guided through the vascular systemof the patient by the guide catheter 24 (which is conventionally placed)to the site of the vascular occlusion that has been determined to exist,so that the rotary working head is located immediately adjacent theupstream end of the occlusion. In the embodiment shown in FIG. 1, theatherectomy catheter is located within a coronary bypass graft 10 havingan upstream end in fluid communication with the aorta 12. The downstreamend of the graft is not shown and is in fluid communication with thecoronary artery being bypassed or with smaller arteries of the heart. Inthe example shown herein the graft 10 is totally occluded by anatherosclerotic lesion or plaque or some other occlusive material 14(FIG. 2) within the interior of the graft.

The atherectomy catheter 22 is introduced into the patient's vascularsystem in a conventional manner, e.g., via the use of the introducersheath and guide catheter. As shown, this is accomplished via apercutaneous puncture 16 in the femoral artery 18. The sheath 26 andguide catheter 24 are each of conventional construction and thus theirdetails will not be described in the interest of brevity.

The working head 32 is arranged to rotate about the longitudinal axis ofthe catheter at a high rate of speed, e.g., from 10,000 rpm to 200,000rpm to repeatedly mechanically impact the occlusive material. At thesame time, an infusate liquid (to be described later) is pumped throughthe atherectomy catheter by a pump (to be described later and forming aportion of the debris removal sub-system 30) and out of distal end ofthe atherectomy catheter adjacent the working head.

The opening of the occlusion to allow freer flow of blood therethroughis effected by impacting surfaces of the rotating working head impactingthe occlusive material 14, whereupon portions thereof are removed, e.g.,broken away. In addition, as will be described later, the rotation ofthe working head produces a powerful, toroidal shaped vortex contiguouswith the working head. This vortex flow has the effect of recirculatingparticles that are broken off from the occlusive material by the impactof the rotary working head's impacting surfaces back into contact withsuch surfaces. Accordingly, those particles are repeatedly impacted,with each impaction reducing the size of the particles further until themajority of resulting particle sizes are very small, e.g., less than 200microns. At the same time another pump (also to be described later) ofthe debris removal sub-system 30 is operated to aspirate the particlesproduced during the revascularization procedure along with the infusateliquid and some blood.

Thus, as will be described in detail later, the debris removal subsystem30 utilizing a downstream balloon, as will be described later, isoperative to ensure that debris produced as the working head opens alumen through the occlusion is not able to flow upstream into theupstream vessel, e.g., the aorta 12, during the lumen opening procedure,and once the working head breaks through or exits the occlusion on thedownstream side, that the debris is not able to flow downstream into thedownstream blood vessel(s).

As best seen in FIG. 4 the atherectomy catheter includes a jacket 34which is formed of any suitable material, e.g., plastic, and has a smalloutside diameter. In the preferred embodiment shown herein, the outsidediameter of the jacket 34 is approximately 1.5 mm (5 French). This sizecatheter is merely exemplary. The means for effecting the rotation ofthe working head is the heretofore identified drive sub-system 28. Thatsub-system is similar to the drives disclosed in the aforementioned U.S.Pat. Nos. 4,686,982, and 4,747,821 and basically comprises anair-turbine motor and associated rotary drive cable (to be describedlater). Other drive systems can be utilized, as well.

Irrespective of the construction of the drive system, it is coupled tothe working head 32 so that the working head is rotated about itslongitudinal axis at the high rate of speed. Many of the details of theworking head will be described later. Suffice it for now to say that theworking head 32 includes an impeller portion 44 and a central shankportion or axle 36 (FIG. 4) projecting proximally therefrom. The axle 36is supported in a central bore of a bushing 38 fixedly mounted at thedistal end of the catheter's jacket 34 by an encircling mounting band40. The shank 36 is fixedly secured to the distal end of a flexibledrive cable 42 forming a portion of the drive sub-system 28.

The impeller 44 forms the distal portion of the working head and isfixedly secured to the shank 36 so that it will be rotated at a highrate of speed about its longitudinal axis by the concomitant rotation ofthe drive cable. The impeller portion 44 comprises a circular disk orbase 52 from which a generally planar tip 54 projects. The tip 54 has apair of generally planar diametrically disposed relieved side surfacesor faces which merge with an arcuate front or distal surface to form apair of arcuate impacting surfaces 54A and 54B. Each of the impactingsurfaces is radiused in a plane perpendicular to the axis of rotation ofthe working head so that each is not sharp, e.g., is in the range ofapproximately 0.001 inch to approximately 0.008 inch, although in thescale of the figures of the drawing they appear to be a sharp line. Theworking head is located within a cylindrical shroud 56 (FIGS. 3 and 4)fixedly mounted on the front of the bushing 38. The shroud 56 includes acylindrical sidewall portion 58 and a generally conical distal wallportion 60 terminating in a circular opening 62 in the distal endthereof. The shroud may be of any suitable outside diameter, e.g., 7 to8 French. The distal arcuate portion of the impeller tip 54 projects outof the central or front opening 62. A side port or open window 64 islocated in the sidewall 58.

As mentioned earlier the system 20 utilizes an infusate liquid toexpedite the revascularization of the vessel. In particular, theinfusate liquid is pumped at a flow rate Q₁ (to be described later) downthrough the interior of the catheter jacket 34 through fourequidistantly spaced grooves 46 extending down the central bore of thebushing 38 and via radial ports 48 to an annular recess 50 in the frontwall of the bushing. The annular recess is in fluid communication withthe side port or window 64 in the shroud so that the infusate liquid canexit therefrom. The direction of flow of the infusate liquid down theatherectomy catheter and out the shroud at its working head is shownclearly in FIG. 4.

The rotation of the working head about its longitudinal axis produces apowerful toroidal shaped vortex flow Q₃ in the fluid contiguous with theworking head. This flow Q₃ circulates by entering into the shroudthrough the central or front opening 62 and exits out through the sidewindow 64 as shown in FIG. 3. Thus, the flow exiting through window 64is Q₁+Q₃. As will be appreciated by those skilled in the art the vortexflow Q₃ has the effect of recirculating any particles that are brokenoff from the occlusive material 14 by the action of the rotating workinghead back into contact with the working head's impacting surfaces. Thus,the occlusive material particles which are broken away are progressivelyreduced in size until they are aspirated by aspiration means forming aportion of the debris removal sub-system 30. That means will bedescribed later. Suffice it for now to state that the aspiration meanswithdraws the infusate liquid, the debris particles and some blood at anaspiration flow rate of Q₂.

As should be appreciated by those skilled in the art the liquid exitingfrom the window 64 of the shroud will tend to push the atherectomycatheter's distal end sideways or laterally in the direction opposite tothe direction of the liquid exiting that window. This hydrodynamicaction may be used to aid in steering the catheter to a desired positionwith respect to an occlusion to be revascularized. In this regard, forexample, when negotiating a branch in the artery system to reach theocclusion to be revascularized, the atherectomy catheter can be rotatedor twisted about its longitudinal axis so that the shroud's window isfacing in the opposite direction to the branch to be entered. Thisaction will cause the side directed liquid exiting the window 64 to pushthe catheter's distal end sideways, whereupon it can enter the desiredarterial branch. Such “hydrodynamic steering” of the atherectomycatheter can be accomplished in other manners and by other means than bythe use of a shroud having a single side window or port. Thus, thisinvention contemplates an intravascular catheter instrument, of anytype, including any means for producing an asymmetric, e.g., sidedirected, fluid flow adjacent the distal end of the catheter so that itcan be steered into a desired position by appropriate rotation of thecatheter about its longitudinal axis.

As mentioned earlier, the guide catheter 24 is of any conventionalconstruction. In the preferred embodiment shown in FIG. 1 it is a 10F to12F catheter having a conventional Y connector 66 at its proximal end.The Y connector 66 has one input leg including a Touhy-Borst adjustablehemostasis valve 66A through which the atherectomy catheter 22 passes.The other input leg, i.e., the angled leg 68, is connected to theaspiration portion of the debris removal sub-system 30 (to be describedlater).

Power for operating the atherectomy catheter is provided by the drivesub-system 28. That system includes an air turbine motor 70 which iscoupled to the proximal end of the flexible drive cable 42. The airturbine 70 is provided with compressed air via an input line or conduit72. Air for the line 72 is provided from a source (not shown) via anassociated regulator 74, and the conventional control valve 76. Thecontrol valve is coupled to the input line 72 of the air turbine. Apressure gauge 78 is connected between the regulator 74 and the controlvalve 76. The regulator 74, the control valve 76, the pressure gauge 78and the associated lines or conduits and the air source make up thedrive sub-system 28. The control valve 76 is of any conventionalconstruction, be it mechanical or electrical. The air turbine motor 70is also of any conventional construction, as is the regulator 74 and thepressure gauge 78. The air turbine includes an outlet port incommunication with the ambient atmosphere, via a line 80. It must bepointed out at this juncture that the atherectomy catheter 22 need notutilize an air turbine motor to rotate the working head. For example, anelectric motor can be provided to replace the air turbine to drive therotating cable and the associated working head.

The debris removal sub-system 30 basically comprises a source 82 of theinfusate liquid “S”, e.g., saline plus a 30% contrast media, a firstpositive displacement pump 84, an input line or conduit 86, an outletline or conduit 88, a second positive displacement pump 90, and a debriscollection vessel 92. The input line 86 and its associated components,i.e., the pump 84 and infisate source 82 serve as the “infusion” meansfor the system 20. To that end the input line 86 is coupled via aconnector to the interior of the atherectomy catheter, i.e., to theannular space within the catheter's jacket between it and the drivecable. The infusate liquid S is pumped at the flow rate Q₁ by thepositive displacement pump 84 through line 86 from the supply or source82. Thus, the infusate liquid S exits the catheter's working head andcirculates as described earlier.

The rate of flow Q₁ of the infusate liquid is established by thepositive displacement pump 84 under control of some automatic or manualcontroller (not shown). In accordance with one exemplary method of usethe pump is operated to produce a flow rate Q₁ the range of 5-80 ml. perminute.

The output line 88 and its associated components, i.e., the pump 90 anddebris collector vessel 92 serve as the “aspirating” means for thedebris removal sub-system 30. To that end, the aspiration line 88 isconnected to the leg 68 of the Y connector 66. The pump 90 is arrangedto be operated to pump the infusate liquid, the debris produced by therevascularization, and some small amount of blood at the flow rate Q₂ inthe proximal direction through the annular space between the atherectomycatheter 22 and the guide catheter 24 and out through the connector leg68 into the outlet line 88, and from there to the collector vessel 92.

The flow rate Q₂ is selected to be greater than Q₁. For example, in oneexemplary method of use the flow rate is selected to be in the range of5-100 ml. per minute, with the differential between Q₂ and Q₁ beingbetween 5 and 50 percent. The use of an aspiration flow rate Q₂ which ishigher than the infusion flow rate Q₁ insures that any debris, e.g.,particles of the occlusive material making up the graft's lesion,produced from debriding that material is positively prevented fromflowing into adjacent vessel portions. In this regard, as will beappreciated by those skilled in the art, since the aspiration flow rateQ₂ is greater than the infusion flow rate Q₁, some blood equal to Q₂−Q₁will also be withdrawn from the upstream vessel, e.g., the aorta asshown in FIGS. 1 and 3. The withdrawal of some blood from that vesselinsures that the debris produced cannot flow upstream to enter into it.Instead the debris particles will be entrained within the infusateliquid and blood which is withdrawn through the aspiration line. Therate of blood withdrawn is preferably be kept to a minimum, e.g., 40 ml.per minute in the interests of patient safety.

In accordance with a preferred aspect of this invention the operation ofthe pumps 84 and 90 are coordinated so that Q₂ is equal to some variabletimes Q₁, where that variable is greater than 1 and is adjustable toaccommodate the needs of the patient. Moreover, the coordination of theflow rates is preferably accomplished automatically, so that a change inone flow rate automatically results in a proportional change in theother flow rate. This coordinated action may be accomplished by amechanical linkage between the pumps, or by a common electricalcontroller for the pumps. Manual control of the pumps is also envisionedfor some applications.

In any case, any suitable positive displacement pumps can be utilized,e.g., peristaltic pumps or piston pumps, in the system.

In order to expedite the revascularization of the bypass graft, theinfusate liquid may be provided with a contrast medium, e.g., 30%contrast medium, so that the revascularization procedure can be viewedusing conventional imaging techniques. Moreover, the infusate liquidcan, if desired, be oxygenated to eliminate distal ischemia when thecatheter is used for arterial restriction opening procedures. Also, ifdesired, small amounts of heparin, urokinase, etc., or other drugs canbe added to the infusate liquid for the procedure.

As should be appreciated from the foregoing the subject inventionprovides a viable means for effecting the revascularization of partiallyor totally occluded coronary bypass grafts, while assuring that anydebris particles produced during the revascularization procedure isremoved from the patient's body. In addition, the subject invention issuitable for revascularizing other occluded vessels, as well. Forexample, in FIG. 5 the system is shown in use revascularizing a totallyoccluded femoral artery 18 downstream of the profunda femoris 18A. Inthis application the system functions to capture the debris createdduring the lumen opening procedure by preventing it from going alongside the catheter and exiting down the profunda to end up in the distalcapillary beds. In this application, a portion Q₄+Q₁−Q₂ of the bloodflowing down the femoral artery 18 to the situs of the occlusion will bepermitted to flow into the profunda femoris, while the portion Q₂−Q₁ ofthe blood and infusate liquid is diverted and/or withdrawn into theguide catheter to ensure positive debris removal in the same manner asdescribed earlier. For some persons, e.g., diabetics with severelycompromised distal capillary beds, a femoral artery revascularizationprocedure is likely to prove beneficial.

Turning now to FIGS. 6A and 6B, an alternative embodiment 100 of thesystem of the subject invention is shown. The system 100 is similar inmost respects to system 20 described heretofore. One major difference,however, is that the atherectomy catheter is arranged for use over aguide wire (to be described later). The guide wire includes a debrisblocking member, e.g., an inflatable balloon (also to be describedlater). When the atherectomy catheter is in place on the guide wire theballoon is located distally of the working head of the atherectomycatheter and the balloon serves to physically block any debris producedby the system 100 which may tend to escape extraction from flowingdistally. The atherectomy catheter used in the system 100 is designatedby the reference numeral 22′ and is identical in most respects to thecatheter 22 described heretofore. In the interests of brevity, thefeatures common to catheters 22 and 22′ will not be reiterated. So too,the features common to systems 100 and 20 will also not be reiterated.Moreover, in the interests of drawing simplicity common components willbe given the same reference numerals.

As can be seen in FIGS. 6A and 6B, the system 100 includes a controlleror console 102 housing the heretofore identified infusate pump 84 andthe extraction pump 90. Each of these pumps is a peristaltic pump. Theconsole 102 also includes a flow control section 104 for establishingthe various fluid flows of the system, as will be described later, and aspeed control section 106 for establishing the operational speed of theworking head of the atherectomy catheter. The details of the speedcontrol section 106 will also be described later. A perfusate pump 108is also provided in the console 102. The perfusate pump 108 is also aperistaltic pump and its operation will be described later. Suffice itfor now to state that the pump 108 is arranged to provide a perfusionliquid, e.g., blood or a suitable synthetic oxygenation liquid,downstream of the inflatable balloon to perfuse downstream (distally)located tissue. The pump 108 also serves to effect the inflation of theballoon.

Compressed gas (e.g., air or nitrogen) is provided via line 72 from theconsole 102 to the catheter's turbine 70. The console, in turn, receivesthe compressed gas from a tank 110 via an input line 112. The rotationalspeed of the turbine is controlled by the speed control section 106 ofthe console 102. On/off operation of the turbine is controlled by aturbine foot control pedal 114 and an associated gas line 116 connectedto the console. This pedal also initiates operation of the infusate pump84.

The speed control section 106 of the console includes a rotary knob forestablishing the desired rotational speed of the turbine and anassociated digital display for displaying the turbine's speed. Theconsole also includes an on/off switch 118 for enabling electrical powerto be provided to the system's electrical components when the switch isin the “on” position.

The foot pedal 114 is used by the operator of the system 100 to initiateoperation of the infusate pump to cause the infusation liquid to flowdown the guide wire and out its distal end and to start the atherectomycatheter's turbine 70 a short time, e.g., 2 seconds, after the infusateliquid begins to flow. The use of the foot pedal frees the operator'shands for other purposes.

The perfusate pump 108 is connected via an input line to a bag 120containing the perfusion liquid. The output of the perfusate pump 108 isprovided via a line 122 to the guide wire of the system 100. The guidewire is designated by the reference numeral 124 and includes theheretofore identified balloon. That balloon is designated by thereference number 126 and, as seen clearly in FIGS. 6B, 7 and 8, islocated adjacent the distal end of the guide wire 124.

The atherectomy catheter 22′ is an “over-the-wire” type of device. Thus,it includes a central lumen for receipt of the guide wire 124 so thatthe catheter 22′ can be threaded over the guide wire 124. The guide wire124 serves to perfuse distally located tissue and to inflate its balloon126 so that the balloon blocks any particulate material (debris) fromflowing distally. To accomplish these functions, the perfusate liquid inthe bag 120 is pumped by the perfusate pump 108 through the line 122 andthrough the interior of the guide catheter 124 where some of it fills orinflates the balloon and the remainder exits at the distal end of thecatheter to perfuse downstream tissue, as will be described later.

The rate of flow of the infusate, extraction and perfusate liquids isestablished by the flow control section 104 of the console via itsvarious up/down switches and associated digital displays. As discussedearlier, the ratio of the infusate flow rate to the extraction flow rateis adjustable. This is accomplished by the appropriate setting of the“infusate flow” and “ratio” up/down switches of the flow control sectionof the console. The desired ratio and the infusate flow rate aredisplayed by the associated digital displays.

In FIG. 7 there is shown in greater detail the distal end of theatherectomy catheter 22′ located within a diseased bypass graft, e.g., are-occluded mammary artery 10′. The diseased artery leads to a distalblood vessel 15, i.e., the vessel to be fed by the graft 10′. The guidewire 124 is in the form of an elongated flexible member, whoseconstruction will be described later with reference to FIG. 8. Thedistal end of the guide wire 124 is in the form of a somewhat soft orflexible, precurved tip 128. The free end of the catheter's tip is ahemispherical dome 130. The balloon 126 is disposed slightly proximallyof the free end 130 of the guide wire 124.

In FIG. 8 the details of the distal end of the guide wire 124 andballoon are shown (although the tip 128 is shown being linear in theinterest of drawing simplicity). Most of the length of the guide wire,i.e, from its proximal end to the location of the balloon 126, is in theform of a two start helical spring 132 (see FIG. 8) whose convolutionsare in close engagement (abutment) with one another. The spring 132enables the guide wire to be bent through a small radius of curvature tofacilitate its intravascular placement via the conventional guidecatheter 24. Inside the helical spring 132 is a liquid impervious, e.g.,rubber or plastic, flexible liner tube 134. This tube prevents theegress of the perfusate liquid through the interface between successiveconvolutions of the helical spring 132 as that liquid is pumped down theguide wire 124.

A perforated support tube 136 is mounted within a distal end helixtermination 138 of the spring 132. The support tube 136 is arranged tomount the balloon 126 thereon and includes a plurality of radiallylocated apertures or ports 140. The balloon 136 is an annular member ofany conventional construction, e.g., rubber, and is mounted on and isdisposed about opposite ends of the perforated support tube 136. Inparticular, the balloon 136 is held in place and sealed to the peripheryof the support tube at each end thereof via respective bands 142. Eachband 142 extends about one cylindrical end of the balloon. Thus, whenthe perfusion liquid is pumped down the guide wire 124 by the pump 108it passes through the apertures or ports 140 (as shown by the arrows inFIG. 8) to fill up, i.e., inflate, the balloon 126.

The distal end of the perforated support tube is located within a springhelix termination 144 forming the proximal end of the guide wire tipportion 128. The portion 128 is also formed as a two start helix, likeportion 132. However, no fluid-impervious sleeve is located within thetip portion 128 so that the interface between successive convolutions ofthe spring forming the tip portion 128 serve as passageways throughwhich the portion of the perfusion liquid which doesn't enter theballoon exits the guide wire as shown by the arrows 146 in FIG. 8.

Since the atherectomy catheter 22′ is designed for over-the-wire use,the drive cable for rotating its working head is in the form of a spiralspring helix having a central lumen extending down its center. Theproximal end of the drive cable is connected to the output of theturbine 70 while the distal end is connected to the working head. Thatworking head is designated by the reference number 32′ and is shown inFIGS. 6A and 7. The central lumen of the spiral helix drive cable formsthe passageway for receipt of the guide wire 124. If desired ananti-friction sleeve or some other anti-friction bearing can be providedat the interface between the inner surface of the spiral drive cable andthe outer surface of the guide wire. The working head 32′ is similar inconstruction to the working head 32 of system 20 except that the workinghead 32′ includes a central bore 148 through which the guide wire 124extends. As can be seen clearly in FIG. 7, the working head 32′ isunshrouded, i.e., is not located within a shroud like the working head32 of the atherectomy catheter 22.

Operation of the system 100 is as follows:

The guide wire 124 with its balloon 126 deflated and with theatherectomy catheter 22′ mounted thereon so that the balloon 126 and tipportion 128 extend beyond the working head 32′ is threaded through apreplaced guide catheter 24 in the patient's vascular system until it isat a desired situs, such as at the arch of the aorta. At this point theguide wire 124 is advanced with respect to the atherectomy catheter 22′so that the guide catheter crosses the lesion or atheroscleroticdeposits in the bypass graft 10′. The precurved tip of the guide wire124 facilitates the placement of the guide wire. In this regard, theguide wire can be rotated about its longitudinal axis to point the tip130 in the desired direction.

Once the guide wire 124 is at the desired position, such as shown inFIG. 7, the balloon 126 can be inflated and the distally located tissueperfused. The exiting perfusion liquid is shown by the arrows in FIG. 7.In particular, the perfisate liquid is pumped by pump 108 and associatedconduit 122 through the hollow interior of the guide wire 124, so thatit passes through the apertures or ports 140 in the support tube 136 toinflate the balloon 126 to the state shown in FIG. 7, while theremainder of that liquid flows out of the open distal end of the supporttube 136, into the hollow interior of guide wire's tip 128, and outthrough the interface between the immediately adjacent convolutions ofthe tip. Accordingly, distally located tissue is oxygenated,notwithstanding the fact that the balloon is inflated and thus blockingthe flow of blood through the bypass graft 10′. If no perfusion oroxygenation of distally located tissue is desired, the system mayutilize an alternative guide-wire mounted debris-blocking balloon. Thatalternative embodiment of the guide-wire is designated by the referencenumber 124′, is shown clearly in FIG. 14, and will be described indetail later.

The rate of flow of the infusate liquid is set by the flow controlsection switch and the ratio of that flow to the extraction flow rate isestablished by the ratio control switch of the flow control section.Accordingly, when ready the operator presses the foot pedal 114 to startthe infusate pump. This action provides the infusate liquid through line86 and through the associated components of the catheter 22′, whereuponthe infusate liquid exits from the catheter at the working tip 32′ asdescribed earlier. The rate of extraction of liquid through the annularspace between the inner surface of the guide catheter 24 and the outersurface of the atherectomy catheter 22′ is established by the extractionpump 90 under control of the associated flow controls of the console:

The turbine 70 is arranged to commence operation on a fixed time delay,e.g., 2 seconds, after the infusate pump commences operation in responseto the depression of the foot pedal 114. This action causes the workinghead to begin rotating at a high rate of speed. The desired speedsetting for the turbine is established by setting of the rotary knob ofthe speed control section of the console. Preferably some restrainingmeans (not shown but like the cradle assembly of the system 200 to bedescribed later) is used to hold or clamp the guide wire in positionwhen the atherectomy catheter is operated to prevent the rotation of theworking head 32′ from causing the guide wire to rotate. The compressedgas e.g., nitrogen or air, powering the turbine 70 of the atherectomycatheter 22′ vents to the atmosphere via line 80. The debris particlesproduced by the rotary working head repeatedly impacting the plaque orother deposit within the diseased graft are withdrawn by the extractionpumps into the collection bag 92, in the same manner as discussedearlier. Any debris particles which may have otherwise escaped beingwithdrawn from the patient's body by the extraction subsystem arepositively prevented from flowing distally by the barrier established bythe inflated balloon 126. Thus, such particles will eventually beextracted. After the diseased bypass graft has been opened, the balloon136 can be deflated by turning off the infusation pump. Then, theatherectomy catheter 22′ and the guide wire 124 can be removed throughthe guide catheter 24.

It must be reiterated that the atherectomy catheter for producing thelumen through the vascular occlusion need not be a rotary impactingdevice, like described above. Thus, a system constructed in accordancewith any embodiment of this invention may make use of any instrumenthaving any type of working head, e.g., a reciprocating impacting workinghead, a combined rotary and reciprocating impacting working head, arotary cutting head, a reciprocating cutting head, a rotary abrasivehead, etc., to open the lumen in the occlusive material in the bloodvessel. Moreover, the working head need not be shrouded. In fact, any ofthe heretofore identified prior art atherectomy devices can be utilizedas part of the system 20 or 100. Some thrombectomy devices may also beutilized as part of the system 20 or 100 (or even as part of the systems200 and 500, to be described later). One such potential device is theAmplatz Thrombectomy Device designated by the trademark CLOT BUSTER byMicrovena Corporation. It should also be pointed out that the workinghead of the device for forming the lumen need not even engage theocclusive material, so long as its lumen-opening operation producesdebris particles to be removed. Thus, devices making use of liquid jets,laser beams, etc., can be utilized to open the lumen as part of thesystem of this invention. In short, any type of instrument for opening alumen through the occlusive material and which produces debris canbenefit from use in the system of this invention, i.e., a system whichestablishes a differential flow, wherein the infusate flow is less thanthe aspiration flow so that particles or pieces of occlusive materialremoved are positively precluded from flowing into adjacent vessels.Moreover, while the production of a local vortex flow adjacent theworking head is desirable to effectuate the lumen opening process and toreduce debris particle size, it is not crucial to this invention.

In the embodiments described in FIGS. 1-8, it has been assumed thatthere will be some blood flow from the patent upstream blood vessel,e.g., the aorta in the case of a revascularization of a bypass graft,which may flow about the exterior of the distal end of the guidecatheter 24 to merge with the flow being drawn into the passagewaybetween the guide catheter 24 and the atherectomy catheter 22. See forexample, FIG. 7 wherein blood flow Q₂−Q₁ from the aorta flows around theouter surface of the distal end of the guide catheter 24 between theguide catheter and the inner wall of the bypass graft 10′. In the eventthat blood flow from the upstream, patent artery, e.g., the aorta 12, isprecluded from entering the guide catheter 24, such as by the outerperipheral surface of the distal end of the guide catheter 24 tightlyengaging the inner periphery of the bypass graft 10′ to berevascularized, care must be taken to control the ingress and egressflow rates with respect to each other to ensure that the bypass graftdoes not collapse since the extraction or aspiration rate will exceedthe infusion rate. As will be appreciated by those skilled in the art,if the bypass graft does collapse, the rotating working head 32 will beforced against the inner surface of the bypass graft wall, which is nowin a flatulent state, and the risk of vascular damage will increase.

In prior art devices, such as the Clement et al. U.S. Pat. No. 5,681,336the potential for vessel collapse is even more acute. In this regard,the Clement et al. patent positively seals off a space in the vessel tobe revascularized between a pair of balloons. In particular, one balloonis located on the distal end of a guide wire distally of the restrictionto be opened and the other balloon is located on the distal end of aguide catheter through which a rotary ablation catheter extends. Thus,when suction is applied to that space to evacuate the particles producedby the revascularization process, if the extraction rate is notprecisely controlled and coordinated to the infusion rate, vesselcollapse may occur to bring the vessel wall into the rotating burr.

The subject invention overcomes this potential vascular collapseproblem. In particular, in FIGS. 9-13 there is shown another alternativeembodiment of a system 200 constructed in accordance with this inventionutilizing an atherectomy catheter 22″ for revascularizing occludedvessels, e.g., coronary bypass grafts. The system 200 obviates theproblem of potential vessel collapse by providing automatic access toblood flow from a patent, upstream vessel, e.g., the aorta 12, via useof at least one flow control or regulation port in the wall of the guidecatheter 24 (or any other tubular member through which the atherectomycatheter 22″ extends and through which the infusate liquid, blood anddebris will be aspirated). The flow control or regulation port(s)extend(s) through the wall of the guide catheter 24 close to its distalend, yet is(are) located sufficient proximally from the distal end ofthe guide catheter so that when the guide catheter is in its normalposition for enabling an atherectomy catheter 22″ (to be describedlater) to revascularize the restricted vessel, e.g., a coronary bypassgraft 10′, the side port(s) is(are) in direct fluid communication withthe blood flowing in the patent upstream vessel, e.g., the aorta 12. Inthe exemplary embodiment of the system 200 shown in FIGS. 9-13 two suchside flow regulation ports 24A and 24B are provided near the distal endof the guide catheter 24. As will become apparent later the size,location and number of flow regulation side ports used is a matter ofchoice, depending upon various system parameters. For example, for asystem making use of a guide catheter of 9 French (one suitable size foreffecting the revascularization of coronary bypass grafts), two sideports 24A and 24B, each of 0.032 inch, may be used. Alternatively, onlyone side port 24A of 0.04 inch. may be used. Other number(s) and sizesof side port(s) can be used as well.

Since the two side ports 24A and 24B extend through the wall of theguide catheter 24, they are in fluid communication with the interior ofthe guide catheter, and hence with the annular space or passagewaybetween the inner surface of the guide catheter 24 and the outer surfaceof the atherectomy catheter 22″ which extends through the guidecatheter. As described earlier it is through this annular space orpassageway that the infusate liquid, blood and any debris, e.g.,atherosclerotic plaque produced by the revascularization procedure, isextracted by the extraction subsystem.

The use of at least one flow regulation or control port ensures that thevessel being revascularized does not collapse as the debris isextracted, even if the guide catheter 24 is tightly fit within thebypass graft 10, such as shown in FIG. 10, and even if the extractionpump 90 is operating at a much higher rate that the infusate pump 84.This automatic control or regulation provided by the at least one sideport(s) will be described after a brief background discussion. To thatend, as will be appreciated by those skilled in the art, if the guidecatheter 24 (or other tubular member through which the atherectomycatheter extends) does not tightly fit in the bypass graft (such asshown in FIG. 11), blood from within the aorta 12 may flow around theoutside of the guide catheter 24 (see the arrows Al) to join with theblood, debris particles and infusate fluid flowing into the open end ofthe guide catheter (see the arrows A2). Accordingly, the action of theextraction pump to remove liquid from the space in the bypass graftsection between the end of the guide tube and the distally locatedblocking balloon 126′ (forming a portion of the guide-wire 124′ to bedescribed later), will not collapse that vessel section, even if theguide catheter does not make use of any flow control or regulation sideport(s). If however, a guide catheter without any flow control orregulation side ports is tightly fit within the bypass graft, thepossibility for vessel collapse exists if the extraction rate is notcontrolled precisely with respect to the infusion rate as discussedearlier.

By utilizing at least one flow control or regulation side port thispotential hazard can be eliminated since such port(s) will provideautomatic access to blood flow in the upstream, patent vessel. In thisregard, as can be seen in FIG. 10, with the guide catheter 24 in placetightly engaging the periphery of the bypass graft section 10′ bloodfrom the aorta 12 is enabled to flow into the flow control regulationports 24A and 24B as shown by the arrows A1. This blood then merges withthe flow (shown by arrows A2) of blood, infusion liquid and debrisparticles produced by the action of the rotary working head 32″ in thebypass graft section between the distally located blocking balloon 126′of the guide wire 124′ (a variant of guide-wire 124 and which will bedescribed later with reference to FIG. 14) and the distal end of theguide catheter 24. By appropriate sizing of the flow control sideport(s) one can ensure that the pressure within the vessel beingrevascularized, e.g., the bypass graft, is positive, thus ensuring thatthe vessel section will not collapse.

The foregoing automatic flow control feature of this invention rendersit useful with other revascularization systems than those of the systemsdisclosed herein. For example, a guide catheter 24 having at least oneflow control port (or any other tubular member through which anatherectomy catheter is extended) can be used with any prior artatherectomy catheter system, e.g., the atherectomy system of theheretofore identified Clement et al. U.S. Pat. No. 5,681,336.

As discussed previously, it is desirable to operate the extraction pumpat a rate to pull more fluid out of the vessel section beingrevascularized than the rate at which infusion liquid is introduced bythe infusion pump to ensure that debris is removed even. By the use of aguide catheter 24 having at least one flow regulation port, like thatdescribed above, one can accept a significant mismatch in flow betweenthe infusate flow and the extraction flow and still not risk collapse ofthe vessel being revascularized. This factor considerably simplifies theamount of coordination between the extraction pump and the infusionpump.

As mentioned earlier the size of the port or ports is a function ofvarious system parameters. In particular, it may be calculated using thefollowing mathematical formulae.

Pressure loss (P2−P3) through the space between the guide catheter andthe working catheter is viscous and is given by the following “Equation(1)”:$\left( {{P2} - {P3}} \right) = \frac{\left( {{Q1} + {Q2} + {Q3}} \right) \cdot L \cdot \mu \cdot e}{1.81 \cdot 10^{6} \cdot \left( {D\left( \frac{\left( {{D1} - {D2}} \right)}{2} \right)} \right)^{3}}$

Where:

Q1+Q2+Q3=flow in³/sec;

D1=Guide catheter inner diameter (inches);

D2=Working catheter outer diameter (inches);

L=Guide catheter length (inches);

P2=vessel pressure (psi);

P3=vacuum source pressure (psi);

e=eccentricity factor, D1 rel. to D2.

Thus, for example, if:

L=41 inches;

D1=0.098 inches;

D2=0.067 inches

μ=3.25 centipoise

e=1.5 if D1 touches D2.

Then Equation (1) becomes$\left( {{P2} - {P3}} \right) = {\frac{\left( {{Q1} + {Q2} + {Q3}} \right)}{7.31}\quad \left( {{{if}\quad {Q1}},{Q2},{{Q3}\quad {mL}\text{/}\min},\quad {{{P2}\quad\&}\quad {P3}\quad {in}\quad {{psi}.}}} \right)}$

The pressure loss through the bypass port(s) has non linear relationshipto flow as set forth in the following “Equation (2)”:

Q 2=90,950.0·Ab·(P 1−P 2)^(0.5)

Where

Q2=flow mL/min

Ab=bypass port area in²

P1=aorta (or upstream patent vessel) pressure psi.

P2=vessel pressure psi.

Equations (1) and (2) assume that there is a tight fit between the outersurface at the distal end of the guide catheter 24 (so that blood fromthe upstream, patent vessel cannot flow past the distal end of the guidecatheter, as is the case shown in FIG. 7) and the total flow of blood,infusion liquid, and debris into the open end of the guide catheter isvery low. Moreover, the calculations for the size of the control orregulation port(s) which follow is based on the assumption that theextraction pump 90 is not satisfied for flow and therefore has sucked orevacuated down to its limit of 27 inches of mercury, whereupon itfunctions as a vacuum source, rather than a flow source.

Equations (1) and (2) can best be solved graphically. To that end, thegraph in FIG. 15 shows the solutions to pressure and flow for severalsizes of flow regulation port(s) and for the guide catheter 24 usingEquations (1) and (2). The intersection of the curves for the twoequations represents the solution to those equations. Thus, it will beseen from the graph that the solutions for the equations with a guidecatheter 24 having a pair of side ports 24A and 24B, each of 0.032 inchdiameter, or a single side port 24A of 0.040 inch diameter, result inpositive pressures, i.e., pressure above venous pressure. Consequentlythe portion of the restricted vessel, i.e., bypass graft section 10′,between the distal balloon 136 and distal end of the guide catheter 24will not collapse. However, where only one side hole or port is used andthat port is either 0.032 inch diameter or of 0.025 inch diameter, anegative pressure will result in the bypass graft section 10′, so thatthe vessel section could collapse.

It must be pointed out at this juncture that the foregoing examples areonly a few of many that are possible to provide automatic protectionagainst vessel collapse utilizing any number of side ports of variousdimensions. Other factors which may be considered in the choice ofnumber, shape and location of the at least one side port, are thedesired structural integrity of the distal end of the guide catheter atthe location of the side port(s), and the possibility of side portblockage by a portion of the wall of the patent upstream vessel or thewall of the vessel section being revascularized.

In FIGS. 9A, 9B, 12 and 13 there are shown the details of system 200.That system basically comprises the same system as the system 100 shownin FIGS. 6-8 described heretofore, with some slight minor modifications(as will be described later). Thus, in the interest of brevity, thecommon components of those systems will be given the same referencenumbers and their construction and operation will not be reiterated.

The system 200 basically comprises a guide catheter 24, a modified guidewire 124′ with a distally located inflatable balloon 126, an atherectomycatheter 22″ with a distally located rotary working head 32″ disposedover the guide wire and within the guide catheter to be movedlongitudinally with respect thereto, a drive sub-system 28 for rotatingthe working head 32″, a cradle assembly 202 (FIG. 9A) for supporting theturbine and associated portion of the drive sub-system, for fixing theposition of the guide wire 124 and guide catheter 24 and for enablingthe atherectomy catheter 22″ to be moved longitudinally with respect tothe guide catheter and the guide wire, a source 110 of compressed gas,e.g., nitrogen or air, to power the drive sub-system, a debris removalsub-system 30 made up of an extraction pump 90 and associatedcomponents, and a control console 204.

The guide wire 124′ is shown clearly in FIG. 14 and is similar to theguide wire 124 in that it includes an inflatable balloon 126′ locatedimmediately adjacent the distal end of the guide wire 124′, a flexibledistal end portion 128′ immediately distally of the balloon 126′ andterminating in an atraumatic tip 130′ at the distal end of theguide-wire 124′. However, the guide wire 124′ is not arranged to perfusedownstream tissue, as is the case of the guide wire 124. Thus, as can beseen in Fin 14 the guide wire 124′ basically comprises an elongatedsmall diameter, flexible, hollow wire or tube 180, e.g., a “hypo” tubeformed of type 304 stainless steel having a 0.010 inch outside diameterand a 0.005 inch inside diameter. A central passageway or bore 180Aextends the full length of the guide-wire tube 180.

The balloon 126′ is formed of any suitable material, e.g., latex of athickness of approximately 0.006 inch, and is fixedly secured slightlyproximally of the distal end portion of the tube 180 via a plurality ofloops or lashes of a filament 182, e.g, polypropylene, wrapped about thetubular proximal end portion 184 of the balloon 126′ and similar loopsor lashes 182 wrapped about the tubular distal end portion 186 of theballoon 126′. This creates a confined space within the balloon and intowhich an inflation gas, e.g., carbon dioxide, is to be provided via theguide-wire tube 180 to inflate the balloon. To that end plural gas ports180B extend through the wall of the .guide-wire tube 180 incommunication with the interior of the balloon and with the centralpassageway 180A in the guide-wire tube 180. The balloon can be anysuitable size, depending upon the application. For example, forrevascularizing a typical bypass graft, the outside diameter of theballoon when deflated may be approximately 0.03 inch, and may beinflated to an outside diameter of up to 0.2 inch (5 mm).

A tapered, flexible, core wire 188, e.g., type 304 stainless steel, issoldered by any suitable lead-free solder into the distal end of thecentral passageway 180A of the guide-wire tube 180 to seal its distalend. A tight helix or coil 128′ is also soldered by a lead-free solderto the outer surface of the distal end of the tube 180. The coil 128′forms the curved, flexible distal end of the guide-wire and can befabricated of any suitable radiopaque material, e.g., platinum wire of0.003 inch diameter. The coil 190 extends for a short distance, e.g.,approximately 1 inch, from the end of the tube 180 and is of a suitablysmall outside diameter, e.g, 0.018 inch. The distal end of the core 188extends into a small bore in the atraumatic tip 130′ and is soldered inplace by a lead-free solder. The distal end of the coil 128′ is alsosoldered to the atraumatic tip by a lead-free solder. The atraumatic tip130′ is in the form of a hemisphere of any suitable material, e.g., type300 stainless steel.

A small sleeve or ring 190 formed of any suitable material, e.g.,plastic or stainless steel, is located on the guide wire 124′immediately proximally of the balloon 126′. This ring serves as a stopmember for the atherectomy catheter 22″. In particular, as theatherectomy catheter 22″ is advanced along the guide wire 124′, with theguide wire 124′ and the guide catheter 24 being held in a fixed positionwith respect to each other and to the patient's vascular system by acradle assembly (to be described later), the rotating working head 32″will be prevented from engaging and perforating the distally locatedballoon by the ring or stop 190. Thus, the advancement of the workinghead along the guide wire to remove the plaque or otherrestriction-forming material in the vessel will not present any dangerof perforating the balloon.

The console 204 is similar to console 102 described heretofore andincludes various electrical and electronic components, e.g., amicroprocessor and associated circuitry to accomplish the variousfunctions of the system and to display various system parameters. Thus,as can be seen clearly in FIG. 9B, the console 204 includes theheretofore identified peristaltic infusion pump 84 and the peristalticextraction pump 90. Compressed gas, e.g., nitrogen, is provided via line112 from the tank 110. The tank provides the compressed nitrogen viaheretofore identified regulator 74 and associated valve 76 into line 112and from there to line 72. The gas pressure is displayed on a dial ormeter 78 on the front of the console. Control of the turbine'srotational speed is effected by a turbine speed adjustment knob 206 onthe front console. The turbine's speed is displayed on a digital displaypanel 208. An optical signal indicative of the turbine's speed isprovided via a fiber optic line 210A. This line is connected to aconnector 212A on the console. Another fiber optic line 210B isconnected to another connector 212B on the console, whereupon a beam oflight from the console is carried down line 212B to the turbine rotorwhere it is broken or chopped up by the rotating blades. The chopped uplight beam which is indicative of rotor speed is carried back to theconsole via line 210A and connector 212A. Control of the turbine iseffected via a turbine foot control (or hand control, not shown) 114connected via line 116 to a connector 214 on the console.

A pressure transducer 218 (FIG. 9A) is connected in the line 86 coupledfrom the infusate pump 84 to the atherectomy catheter 22″. The pressuretransducer provides an output signal via a line 220 to a connector 222(FIG. 9B) on the console. The rate of infusion liquid flow into theatherectomy catheter 22″ is effected by the heretofore identifiedperistaltic pump 84. The speed of that pump is controlled via an up/downswitch 224 on the console. The pump's speed in RPM is displayed on adigital readout panel 226. The speed of the extraction pump iscontrolled by an up/down switch 228 on the console and that pump's speedis displayed on an associated digital readout panel 230. The consolealso includes an on/off switch 232 for providing electrical power to thesystem when the switch is in the on position.

Data from the console, e.g., operating parameters, etc., is arranged tobe downloaded to any suitable device, e.g., a laptop computer 216, viaconventional multipin electrical connector 218, e.g., an RS 232 serialport, and associated cable 220.

If desired, the console 204 may also include various alarm devices towarn operating personnel of certain abnormal conditions. For example,the console may include a low battery power warning lamp on the front ofthe console to warn operating personnel that the battery is low. Aninfusate high pressure warning lamp may also be provided on the consolealong with an associated audible annunciator to produce respectivevisible and audible warning signals when a high pressure infusatecondition exists.

Referring now to FIGS. 12 and 13, the details of the atherectomycatheter 22″ will now be described. As can be seen that the catheter 22″is similar to catheter 22′ in that it includes a jacket 34 having adistal end. A rotary working head or tip 32″ is located at the distalend of the jacket. The tip 32 is preferably constructed in accordancewith the teachings of U.S. Pat. No. 4,747,821. However, tip 32″ unlikethe tip of the aforementioned patent includes a central passageway orbore 148 through it (like tip 32′). It is through this bore that theguide wire 124 extends.

The working head 32″ is mounted for rotation within a bushing 302secured to the distal end of the jacket. The bushing 302 is similar inconstruction to the bushing of the U.S. Pat. No. 4,747,821 and itincludes plural passages 46″ extending along its length through whichthe infusate liquid passes to exit out of the tip. In addition itincludes plural radial passageways 304 in the thrust pad portion formingthe distal end of the bushing and which are in communication with thepassages 46″ through which the liquid exits radially. The radialpassages are constructed similarly to those of U.S. Pat. No. 5,049,124(Bales, JR) whose disclosure is incorporated by reference herein. Thus,the exiting liquid from those passages is impacted by the flattenedsides of the tip to create a vortex flow in a manner similar to that asshown in FIG. 12. The rotary working head 32″ also includes a tubularshank portion through which the central bore 148 extends. Infusateliquid from the passageway 312 is enabled to flow into the open proximalend of the bore 148 and through the annular space or clearance betweenthe inner surface of that bore and the outer surface of the guide wireextending through the bore as shown by the arrows in FIG. 12. A sleeve306 is located immediately proximally of the bushing 302 and extendsabout the shank portion of the rotary working head 32″. The sleeve 306is welded to the shank portion of the rotary working head. The rotaryworking head 32″ is arranged to be rotated at a high rate of speedwithin the bushing by a drive cable 308. As best seen in FIG. 12, thecable 308 is a bifilar or double helix formed of any suitable material,e.g., 304 stainless steel or Nitinol, and is flexible so that theatherectomy catheter can be readily bent to follow tortuous paths to therevascularization site, i.e., the coronary bypass graft. The distal endhelices of the drive cable 308 are welded at 310 to the shank portion ofthe rotary working head 32″. The outer diameter of the drive cable isless than the inner diameter of the catheter jacket 34 to form anannular passageway 312 therebetween. This passageway extends the fulllength of the atherectomy catheter and serves to carry the infusionliquid to the working head 34″.

A flexible plastic tube or sleeve 314 is located within the centralpassageway of the bifilar drive cable 308 and extends for the fulllength thereof. The tube 314 includes a central passageway 316 which isof approximately the same internal diameter as the bore 148 extendingthrough the working head 32″ and is coaxial therewith in order toaccommodate the guide wire 124 therethrough. The sleeve 314 serves toform a barrier between the metal helices of the drive cable 308 andmetal guide wire extending through it, while preventing the helices ofthe cable 308 from closing up as the drive cable is rotated.

In FIG. 13, there is shown the details of the proximal end of theatherectomy catheter 22″. Thus, it can be seen that the proximal end ofthe jacket 34 is flared outward at 318. The flared proximal end of thejacket is connected to the distal end of a turbine housing or body 320via a capture nut 322. The capture nut 322 includes internal threads 324which mate with corresponding external threads on the distal end of theturbine housing 320. The free end of the turbine housing is tapered at326. The capture nut 322 also includes a tapered inner surface 328merging into a central bore 330 through which the catheter jacket 34extends. Thus, when the nut 322 is tightened, the flared end 318 of thejacket is tightly interposed between the surface 330 of the nut and thetapered surface 326 of the turbine housing 320. The distal end portionof the turbine housing 320 also includes a central bore 332 into whichthe infusate fluid will be injected for flow into the annular passageway312 in the atherectomy catheter, as will be described later.

The proximal end of the bifilar drive cable 308 is connected, e.g.,welded, to an adaptor sleeve 334. The adaptor is a tubular member whichis in turn welded to the turbine rotor drive shaft 336. The turbinedrive shaft 336 is an elongated tubular member. Being tubular theturbine drive shaft 336 includes a central passageway. It is throughthis central passageway that the guide wire is arranged to be extended.The turbine rotor drive shaft 336 extends through the central bore 332in the turbine housing and terminates at its proximal end in aseven-bladed turbine rotor 338. The rotor is located in an enlargedproximally located flanged portion 322 of the turbine housing 320. Inparticular, the flanged portion 322 includes a hollow interior chamber340 in which the turbine blade 338 is located. An enlarged central bore342 extends distally of the chamber 340 and is axially aligned with thecentral bore 332 in the distal portion of the turbine housing 320. Asleeve bearing 344 is located within the central bore 342. The turbinerotor shaft 336 extends through a central bore in the bearing with aslight clearance or leakage passageway, e.g., 0.0005 inch, to form afluid leakage path to facilitate the cooling of the bearing. An O-ring346 is located within an annular recess in the distal portion of thesleeve bearing 344 to form a fluid-tight seal. A star washer 348 islocated within an enlarged portion of the bore 342 to hold the sleevebearing in place.

The proximal end of the turbine drive shaft 336 extends into a ballbearing assembly 350 to center the turbine shaft on the longitudinalaxis of the housing. A guide-wire centerer and leakage controlrestrictor member 352 is located within the hollow proximal end of theturbine drive shaft 336. The guide wire 124 is arranged to pass throughthe restrictor where it is centered and then through the turbine driveshaft, the adaptor 334, the sleeve 314, and out through bore 148 in theworking head 32″. Moreover, air can pass through the interface of therestrictor 352 to cool and lubricate the adjacent surfaces. The ballbearing assembly 350 is held in place via a cap or cover 354. The cap354 serves to close off the hollow interior of the turbine housing. Tothat end, the cap is releasably secured to the flanged proximal portion322 of the turbine housing 320 via plural threaded bolts 356. Anenlarged bore hole 358 is located within the cap 354 and is coaxiallyaligned with the central longitudinal axis of the drive shaft 336. Asmaller diameter bore 360 communicates with the bore 358 and with therestrictor 352.

The compressed gas, e.g., nitrogen, to effect the rotation of theturbine is provided from the tank 110 via an inlet port 362. Thepressurized gas enters the turbine housing portion 322 somewhattangentially and impinges on the angled rotor blades 338 to cause theturbine rotor to rotate about its longitudinal axis at a high rate ofspeed. This effects the concomitant rotation of the drive shaft 336, thebifilar cable 308 and hence the rotary working head 32″.

The infusate fluid, e.g., saline and a contrast medium (plus anythingelse which is desired to be introduced into the vascular system, such asheparin, growth factors, microspheres carrying chemicals,pharmaceuticals or other biologically active materials, etc.) isintroduced into the turbine housing 320 so that it gains ingress intothe passageway 332. From that passageway, it flows through thecommunicating passageway 312 extending within the jacket of the catheterto exit at the distal end of the jacket where the working head 32″ islocated. The means for introducing infusate liquid into the turbinehousing comprises the tubing 86 on which a connector 362 is mounted. Theconnector 362 is arranged to be connected to the output of the infusatepump.

An interlock member 366 is located in a transverse bore 368 in theturbine housing 320 so that it perpendicularly intersects thelongitudinally extending bore 332. The interlock member is a generallyplug-like, tubular body having a thin walled upper end 368 defining anenlarged hollow interior space. An opening 370 is provided in the thinwalled upper end of the interlock member communicating with the enlargedhollow interior space and into which the distal portion of the sleevebearing 344 extends. Another opening 372 is provided diametricallyopposed from the opening 370 so that the turbine drive shaft 336 canextend through the interlock member via the openings 370 and 372. Thelower end of the interlock member 366 includes a barb-like tubularprojection 374 which extends into the interior of the plastic tube 86. Aring-like ferrule 376 extends about the outer surface of the tube at theupper end thereof to capture the tube on the barb. A sealing O-ring 378is disposed within an annular recess extending about the periphery ofthe interlock member 366. The barb portion of the interlock member 366includes a passageway 378 extending through it in communication with thehollow interior at the upper end of the interlock member. Thus, theinfusion liquid introduced into the tube 86 will pass through thecommunicating passageway 378 in the barb member into the hollow upperinterior 368 of the interlock member and out through opening 372 intothe passage way or bore 332. From passage way 332, the infusate liquidwill flow through the hollow annular passageway 312 in the catheter'sjacket 34 and out through its distal end at the working head 32″.

As will be appreciated by those skilled in the art, the rotation of thedrive cable 308 creates an Archimedes-like pumping action to aid theinfusate pump in carrying the infusate liquid down the annularpassageway 312 in the jacket 34. In particular, the ability of thehelical drive cable 308 to deliver flow is a function of: (1) therotation speed of the helix, (2) the swept volume of the helix (theswept volume of the helix being the volume of fluid entrapped betweenthe coils of one pitch of the helix), and (3) the leakage of flow backalong the helix due to the clearance between the helix and the jacketand the clearance between the helix and the liner. If the clearances arereduced to zero (leakage reduced to zero) the pump can act as a verystiff positive displacement pump, that is, it can deliver flow at alarge range of output pressures regardless of the inlet pressure. Forexample, with a 5F diameter catheter having bifilar drive cable with0.008 inch wire diameter and pitch of 0.040 inch running at speedsbetween 100,000 and 160,000 RPM, the helix design suitable fortransmitting suitable torque, with adequate flexibility for navigatingthe bends of the coronary vasculature, also has the correct swept volumeto deliver an appropriate flow, e.g., 30-40 mL/minute, required to keepthe catheter and tip abrasion site at a temperature compatible withtissue viability (e.g., not more than 98 deg F.). These facts make itpossible for a 5F catheter system to use the helical drive cable 308 asthe infusate metering pump while the peristaltic infusate pump 84 servesas a priming pump. This arrangement, can deliver pressure rather thanflow by the use of soft pump tubing, i.e., tubing that leaks back underthe pump 84 rollers, if the delivery pressure becomes excessive, e.g.,approximately 30 psi or greater. If different size catheters are used,such as 8F or 4F, the helical drive cable design may not provide theideal flow, and the peristaltic infusate pump 84 characteristics mightwell have to be changed to obtain the correct flow. This can beaccomplished by changing the peristaltic pump speeds, changing thestiffness of the peristaltic pumps by using tubing of differentsoftness, and partially disabling the helix drive cable pump byincreasing the clearances around the helix. Thus, if the consoleprovides for independently adjustable peristaltic pump speeds for theinfusate and extraction pumps, the system can provide for any catheterdesign. The operator can be instructed to select the appropriate pumpspeed and the appropriate pump tubing for whatever catheter is in use.In some instances it may be advisable to use operator adjustableperistaltic pumps linked electronically that provide for fixed ratiosbetween the infusate and extraction pumps, and in other designs it maybe best to provide for the pumps to be preset and not user adjustable.

It has also been found that there is an advantage to having a variablepitch helix for the drive cable 308. Thus, the cable 308 is preferablyso constructed. As will be appreciated if the drive cable 308 is to actas a pump in addition to the means for effecting the rotation of theworking head, the helices of the cable have to have a certain pitch(e.g., 25 coils to the inch) to provide the required swept volume. Ifthe bending stiffness of the atherectomy catheter is to be minimized(e.g., to enable the catheter to freely negotiate tortuous paths to thesite of the occluded vessel section) the helices of the cable needs tobe approximately of closed coil configuration (e.g., 40 coils to theinch), but not quite closed, because it is best if the coils do nottouch each other as the catheter bends since the friction between theabutting coils may cause excessive heat to be generated. It has beenfound that if the distal end portion of the helical drive cable 308 isalmost close wound for a short distance (e.g., 0.5 to 4.0 inches), as isthe case in the embodiment shown herein, the remainder of the cable,(i.e., the portion located proximally of the distal end portion andwhich may be approximately 50 inches or longer) can force the infusateliquid past the close coils at the distal end and out of the catheter.The variable pitch of the drive cable thus provides for the optimumpumping action, while maintaining optimum flexibility. As will also beappreciated the helix pitch of the drive cable also has an affect onvibration of the catheter, with the coarser or greater spacing betweenhelices resulting in lower vibration. Thus, the variable pitch drivecable 308 will also help to reduce the vibration level by minimizing thelength of closed coil helices at the distal end of the drive cable.

As mentioned earlier, the system 200 includes a cradle assembly 202 forholding the guide catheter 24 and the guide wire 124 fixed with respectto each other and with respect to the patient's vascular system, whilesupporting a portion of the atherectomy catheter to enable it to bemoved longitudinally with respect to the guide catheter and guide wirein order to advance the working head through the vessel section to berevascularized. The cradle assembly 202 will now be described withreference to FIG. 9A. As can be seen therein, the cradle assemblybasically comprises a cradle member 400 (shown by phantom lines in theinterest of drawing simplicity) and other associated components (someshown by solid lines and others by phantom lines), all to be describedlater. The cradle member 400 itself is a generally tubular member whichis arranged to support the turbine body therein and to allow the turbinebody to slide longitudinally with respect to the cradle member 400 whilefixing the position of the guide catheter 24 and guide wire 124 relativeto each other.

The tubular cradle 400 includes a loading slot 402 extending from itsfront or distal end to a point close to its rear or proximal end. A pairof support feet 404, also shown by phantom lines, are provided on theunderside of the cradle tube to support it on any horizontal surface. Acup-shaped plug member 406 is mounted in the open rear end of the cradletube. The plug member includes a central passageway 408 extendingthrough it. A pair of telescoping tubes 410 and 412, are mounted betweenthe central passageway in the plug member and the proximally located cap354 of the turbine housing 320 via a ferrule (not shown). The centralpassageway 408 in the plug member and the associated telescoping tubes410 and 412 provide a passageway through which the guide wire 124 may beextended into the turbine housing and from there through the atherectomycatheter 22″ as described earlier. The telescoping tubes are formed ofany stiff material, e.g., type 304 stainless steel, to prevent bucklingof the guide wire.

In order to fix or clamp the longitudinal position of the guide wirewith respect to the cradle assembly while also forming a fluid tightseal about the guide wire where it enters the plug member 406, aconventional hemostasis valve, e.g., a Tuohy Borst valve 412, is mountedon the rear side of the plug member via a wing nut mount (not shown).

The turbine housing assembly is mounted within the cradle tube forsliding movement therealong in order to adjust the distance that theworking head 34″ extends from the distal end of the guide tube 24. Thisfeature enables the rotary working head to be advanced in the distaldirection to open a lumen through the plaque or other material formingthe restriction in the bypass graft to be revascularized. To achievethat end, a handle 416 is provided for the turbine housing and projectsradially outward from the turbine housing portion 322. The handleextends through a longitudinally extending linear slot 418 in the cradletube 400. It should be pointed out at this juncture that the handle andthe associated slot are shown on the facing side of the turbine tube(i.e., the visible side in FIG. 9), when in reality they are located onthe opposite side. The showing of the handle and slot on the facing sideof the cradle tube is merely done for drawing convenience.

In order to increase the “wheel base” of turbine housing so that itslides easily within the cradle tube 400 in a longitudinal directionwithout tilting or canting, a turbine tube housing extension member 420is mounted, i.e., snap-fit, on the distal portion of the turbinehousing. The extension member 420 includes a central opening throughwhich the atherectomy catheter 22″ exits the turbine housing.

A manifold member 422 is mounted within an extension adjustment tube 424at the front end of the cradle tube 400. The extension adjustment tubeis a slotted tube which telescopes within the front end of the cradletube 400 and whose position can be adjusted so that the manifold 422 canbe moved closer or further away from the cradle tube. This featureenables the system 200 to be used with guide catheters of varyinglengths. In order to fix the position of the extension adjustment tubewith respect to the cradle tube 400, a tube extension latch 426 isprovided to extend through any selected one of plural longitudinallyspaced holes 428 in the extension tube and a single aligned hole notshown in the front end of the cradle tube.

The manifold 422 is a disk-like member having a longitudinal passageway(not shown) extending therethrough and to which the proximal end of theguide catheter 24 is connected via a swivel connector 430. The swivelconnector permits one to adjust the angular orientation of the guidecatheter with respect to the cradle tube so that the guide catheter canbe revolved to any rotary position necessary to obtain compatibilitywith the patient's vascular anatomy. The longitudinal passageway of themanifold is in fluid communication with the proximal end of the annularpassageway 312 extending down the interior of the atherectomy catheter'sjacket. The manifold also includes a radially extending side port (notshown) in communication with the longitudinal passageway at the proximalend of the guide catheter. The extraction (vacuum) tube 88 is arrangedto be connected to the radial side port of the manifold via conventionalconnector 432 to withdraw blood, infusate liquid and debris which hasbeen drawn down the passageway between the guide catheter and theatherectomy catheter by the action of the extraction pump 90.

Since the atherectomy catheter 22″ extends through the guide catheter24, a conventional hemostasis valve 434 is mounted on the rear(proximal) side of the manifold 422 to enable to the atherectomycatheter to extend through the longitudinal passageway in the manifoldand into and through the guide catheter 24.

A stiffener tube 436 is provided on the atherectomy catheter between theturbine housing and the manifold to prevent the atherectomy catheter'sjacket 34 from buckling under axial loads. The stiffener tube alsofacilitates the assembly and loading of the atherectomy catheter intothe cradle tube. To that end, a hook wire 438 is mounted on thestiffener tube 436 to facilitate movement of the stiffener tube. A pairof pivotable trunnions 440 project outward from the distal end portionof the stiffener tube for connection to diametrically opposed portionsof the extension tube 424 to center the stiffener tube so that it can belifted to enable loading of the atherectomy catheter.

In accordance with one preferred embodiment of the invention, thelongitudinally extending slot 402 is of sufficient length to enable theturbine housing and hence the atherectomy catheter 22″ to bereciprocated through a 4-5 inch range.

It must be pointed out again that the subject invention is not limitedto atherectomy catheters, and particularly rotary head catheters. Inparticular, the subject invention may incorporate an instrument havingany other type of working head, e.g., a balloon angioplasty catheter, acatheter for injecting a restriction-removing or dissolving liquid, anultrasonic catheter, a laser catheter, a stent-delivery catheter, etc.,for opening a lumen in an occluded vessel. To that end the term “workinghead” as used herein is meant to include any type of device foroperating on an occluded vessel to open a lumen in that vessel to thefreer flow of blood therethrough.

In FIGS. 16 and 17 there are shown yet another alternative embodiment ofa revascularization system 500 of this invention. The system 500 isarranged to revascularize an occluded blood vessel, e.g., a bypass graft10′, by introducing a conventional expandable stent 502 into a lumenformed in the restrictive material of the occluded blood vessel section,e.g., the bypass graft. If desired, the system 500 may also employ theatherectomy catheter and some associated components of the system 200described heretofore to effect the opening of a lumen through thematerial forming the restriction, followed by the introduction of astent-delivery catheter (not shown) for carrying the stent 502 in acollapsed state into the lumen created by the atherectomy catheter, andthen to expand the stent 502 in that lumen to the state shown in FIGS.16 and 17 to ensure that the lumen stays open. The stent-deliverycatheter used in such an application may be of any conventional type,e.g., a balloon catheter.

It must be pointed out at this juncture that the system 500 may be usedwithout an atherectomy catheter, like the catheters described above orany prior art restriction-opening device, for initially forming thelumen through the material forming the restriction. In such analternative application, as will be described later, the system 500makes use of any suitable conventional stent-delivery catheter to carrythe collapsed stent 502 over a guide wire, like guide-wire 124′ or anyother suitable balloon bearing guide-wire, through the restriction inthe occluded blood vessel to an operative position, whereupon thestent-delivery catheter is operated, e.g., its balloon inflated, toexpand and place the stent in position (like shown in FIGS. 16 and 17).

Irrespective of the manner in which the lumen is created into which thestent 502 is placed, the system 500 of this invention makes use of adebris removal sub-system to remove any particles or other debrisproduced during the revascularization/stenting procedure. That debrisremoval system may be similar to that described earlier, or any othersuitable type. As shown in the embodiments of FIGS. 16 and 17, thedebris removal sub-system used to remove any particles or debrisproduced during the revascularization/stenting procedure basicallycomprises a guide catheter 24 having at least one control port, likethat described above, and another catheter 504 (to be described later)for delivery of an infusate or irrigation liquid from some pumpingmeans, e.g., an infusate pump 84, into the occluded vessel section, andsome pumping means, e.g., an extraction pump 90, coupled to the interiorof the guide catheter 24 to effect the removal of blood, the infusionliquid and any debris created during the restriction opening procedurefrom the patient. It should be noted that the “other catheter 504” fordelivery of the infusate or irrigation liquid to the situs of the vesselportion being revascularized, may comprise an atherectomy catheter 22″like that described with respect to system 200 when such a system isused to form the lumen into which the stent will be placed, or maycomprise a separate catheter, tube, or conduit, or may comprise a lumenor passageway in the guide catheter 24 separate and apart from thecentral passageway through which the debris, blood and infusate liquidis removed. In the embodiment shown the catheter 504 for carrying theinfusion or irrigation liquid into the situs where the stent is to beplaced basically comprises a simple irrigation tube or catheter formedof a flexible material, e.g., a plastic, and having a central passagewayor lumen extending fully therethrough for carrying the infusate orirrigation liquid from a pump, like pump 84 or any other suitable sourceof irrigation liquid, down the lumen and out of its open end to theoperative situs like shown in FIGS. 16 and 17.

If it is desired to utilize a system 500 to apply the stent 502 into alumen formed by an atherectomy catheter, e.g., atherectomy catheter 22″,the procedure to be followed basically comprises the following steps.First the guide catheter 24 is placed in position so that its distal endis located proximally of the restriction to be opened and its control orregulation port(s) 24A/B is(are) in fluid communication with an upstreampatent vessel, e.g., the aorta, like shown in FIGS. 10, 11, 16 and 17.The guide wire 124′ is then extended through the guide catheter 24 andthrough the restriction to be opened so that the distally locatedballoon (obturator) 126 on the guide wire is downstream of therestriction. The balloon 126 is then inflated to block the vessel to berevascularized downstream of its restriction. The extraction pump 90 isthen operated to evacuate any debris particles which may have beenproduced by the passage of the guide wire 124 and balloon 126 throughthe restriction and by the inflation of the balloon 126. The atherectomycatheter 22″ is then passed over the guide wire through the guidecatheter so that its working head 32″ extends out of the open end of theguide catheter and is at the situs of the restriction to be opened.

The atherectomy catheter 22″ (or any other catheter having a restrictionopening working head) is then operated in a manner like described aboveto enable the working head to open a lumen through the restriction,while the debris removal sub-system removes the debris created by thatoperation along with blood and the infusate liquid through the guidecatheter. The control or regulation ports in the guide catheter ensurethat the vessel being revascularized does not collapse during theprocedure.

Once the lumen has been created through the restriction, the atherectomycatheter can be removed, while maintaining the vacuum, i.e., keeping theextraction pump 90 operating. After removal of the atherectomy catheterthe extraction pump 90 can be stopped. If it is desired to give thepatient some recovery time before deployment of the stent 502, thedistal balloon on the guide wire may be deflated, thereby enabling bloodto flow through the newly formed lumen in the revascularized vessel tothe downstream vessel, e.g., a coronary artery 15. Once sufficient timefor the patient to recover has elapsed (assuming that any recovery timeis desired) the distally located balloon 126 is then re-inflated.

The stent-delivery catheter (not shown) is then introduced through theguide catheter and over the guide wire until its working head, e.g., theballoon on which the collapsed stent 502 is located, is within the lumencreated by the atherectomy catheter 22″. The stent-delivery catheter isthen operated, e.g., its balloon inflated, to expand the stent 502radially outward and into seating engagement with the revascularizedvessel section, like that shown in FIGS. 16 and 17. If desired, thedebris removal system may be operated to withdraw any debris particlescreated by the deployment of the stent. Once the stent has been deployedthe stent-delivery catheter can be removed, e.g., its balloon deflatedand then the catheter withdrawn proximally along the guide wire. Theguide catheter can then be removed.

In some applications it may be desirable to provide an irrigation orinfusate liquid into the lumen in which the stent is to be deployedduring or immediately after the stent deployment the procedure. To thatend, an irrigation tube 504 (like that shown in FIGS. 16 and 17) may beintroduced over and along the guide wire 124′ and through the guidecatheter 24 so that its open distal end is in communication with thesitus of the stent while the distally located balloon (obturator) 126′remains inflated. An irrigant liquid can then be introduced via theirrigation tube to flush out any debris via the passageway between itand the guide catheter under the action of the extraction pump 90 or anyother suitable pump or vacuum source. Once this has been accomplishedthe irrigation tube 504 can then be withdrawn over the guide wire, whilethe vacuum is maintained, e.g., the pump 90 operates, to remove anydebris which may be produced by the removal of the irrigation tube. Thevacuum (e.g., pump 90) can then be stopped, the balloon 126′ on thedistal end of the guide-wire 124′ can then be deflated and the guidewire can then be withdrawn through the guide catheter 24. Then the guidecatheter can be removed.

If it is desired to place a stent 502 within an occluded blood vesselsection, without having first opened a lumen through it with anatherectomy catheter, like catheter 22″ or any other lumen-openingcatheter, the procedure to be followed using the system 500 basicallycomprises the following steps. First the guide catheter 24 is placed inposition so that its distal end is located proximally of the restrictionto be opened and its control or regulation port(s) 24A/B is(are) influid communication with an upstream patent vessel, e.g., the aorta,like shown in FIGS. 10, 11, 16 and 17. The guide wire 124′ is thenextended through the guide catheter 24 and through the restriction to beopened so that the distally located balloon (obturator) 126′ on theguide wire is downstream of the restriction. The balloon 126′ is theninflated to block the vessel to be revascularized downstream of itsrestriction. The stent-delivery catheter (not shown) is then introducedthrough the guide catheter 24 and over the guide-wire 124′ until itsworking head, e.g., the balloon on which the collapsed stent 502 islocated is at the desired position within the vessel to berevascularized. The debris removal sub-system, or any other extractionor vacuum system, is then operated to withdraw any debris or particlescreated when the stent is deployed. Thus, once the debris removalsub-system is operating the stent-delivery catheter can then beoperated, e.g., its balloon inflated, to expand the stent 502 radiallyoutward thereby enlarging the lumen through the restriction seating thestent in place against accidental dislodgement within the blood vesselsection, like that shown in FIGS. 16 and 17. Once the stent has beendeployed the stent-delivery catheter can be removed, e.g., its balloondeflated, and then the catheter withdrawn, e.g., slid proximally alongthe guide-wire 124′ until it is out of the being's body. An irrigationor infusate liquid is then provided into the operative situs, i.e., thesitus of the stent, to flush away any debris created during the stentdeployment procedure. To that end, an irrigation tube 504 is introducedalong the guide wire 124′ and through the guide catheter 24 so that itsopen distal end is in communication with the situs of the stent, whilethe distally located balloon (obturator) 126 remains inflated. Anirrigant liquid can then be introduced via the irrigation tube 504 toflush out any debris via the passageway between it and the guidecatheter 24 under the action of the extraction pump 90 or any othersuitable pump or vacuum source.

Once the stent is deployed and all debris removed, the irrigation tubecan then be withdrawn from the being by sliding it out over theguide-wire 124′, while the vacuum is maintained, e.g., the pump 90operates, to remove any debris which may be produced by the removal ofthe irrigation tube. As described earlier, the control or regulationport(s) 24A/B ensure that the vessel section being revascularized doesnot collapse during the revascularization procedure.

After removal of all remaining debris, the vacuum (e.g., pump 90) canthen be stopped, the balloon 126 on the distal end of the guide-wire canthen be deflated and the guide wire can then be withdrawn through theguide catheter. Then the guide catheter can be removed.

Irrespective of the type of revascularization procedure utilized, it maybe desirable before removal of the guide catheter 24 to inject a dyethrough it to the operative situs to enable one to fluoroscope orotherwise visualize the bypass vessel to ensure that it has been beproperly revascularized.

In FIG. 18 there is shown a preferred embodiment of the overall systemof this invention. The components of the overall system are given thesame reference numbers in FIG. 19 as previously used in the interest ofbrevity and consistency. In FIG. 9b the control system for therevascularization device of this invention is shown in the form of aconsole 204. In FIG. 18 the control system equivalent to the console 9Ais denoted by the reference number 600 and is shown mounted on aroll-about unit 602. The control system 600 has a video display 604 withan associated microphone 606 and loudspeaker 608 and various control(mode or procedure) buttons or switches 610. The revascularizationsystem of this invention is arranged to be operated in various modesunder control of the control system. In particular, it has beendetermined that the values selected by the control for infusate pumpspeed would fall into a few groups related to the particular mode ofoperation of the system. It has also been determined that the operatorhas to carry out preliminary functions, such as priming the catheter toeliminate air bubbles, and priming the extraction tubing for the samereason. The operator also has to flush the operative site afterdeployment of a stent.

In accordance with one aspect of this invention the system is arrangedso that the operator can be guided throughout the procedure by the useof simple mode buttons 110 and the video display 604 shown mounted onthe roll-about unit. This arrangement provides information about thesequence of the procedure, the values of important parameters, andprovides the operator with some guidance in the case of faults occurringbased on software included in the system. The table below illustratesthe information that is available to be displayed by selection of themode buttons 610 of the control system 600 console shown in FIG. 18.

Display Foot control Foot depressed control Audible alarm Mode ElapsedInfusate Turbine released sounds button time pressure speed ProceduralTroubleshooting # Mode description Minutes psi KRPM instructionsinstructions 1 Prime catheter & No Yes Yes Yes Yes if alarm test speed 2Prime extraction No No No Yes No 3 Run catheter Yes Yes Yes Yes Yes ifalarm 4 Adjunct therapy No No No Yes No 5 Flush Yes No No Yes Yes ifalarm

It should be noted that the right hand column of the above table denotesthe presence of troubleshooting instructions if an alarm occurs. In apreferred embodiment of this invention an alarm sounds if the infusatepressure is either too low (indicating a starvation of supply to thecatheter and the danger of damaging tissue) or too high (indicating ablockage with similar consequences). The video display 604 could be usedin a similar manner for any other alarms conceived.

In use the operator starts by pressing the “Mode button #1” of thebuttons or switches 610 and follows the displayed instructions. When thefoot control 114 is depressed to activate the pumps 84 and 90 and/or theturbine 70 the display 604 changes to show only the active values oftime, infusate pressure, and turbine speed. If an alarm sounds thedisplay suggests corrective action.

As will be appreciated by those skilled in the art the subject systemcan be expanded to deal with more modes and more signals from additionaltransducers, such as sensors for the degree of filling of the extractioncollection bag 92, or temperature of the catheter at the tip.

One of the significant advantages of this sequential display ofinformation is the ability to use a small display screen and to avoidoverloading the operator with masses of information at once. A furtherimprovement is provided by the subject system including means fordelivering audio instructions to the operator and for accepting voicecommands or information from the operator through the use of voicerecognition means, e.g., hardware and software in the system. Forexample, with such a system, the operator can call out the mode, whichis picked up by a microphone on the console. A voice recognition chipand associated software (not shown) accepts the input, adjustsparameters for pump and turbine speed and then produces audibleinstructions which are delivered to the operator through theloudspeaker. As will be appreciated by those skilled in the art theaudio signals can also be transmitted to the operator by alternate meanssuch as cables, wireless and headphones etc.

In FIG. 19 there is shown a preferred embodiment of the guidewire 124′with the balloon 126′ mounted thereon. In particular, the guidewire 124′includes a wear resistant coating (not shown) on its outer surface topreclude the risk of damage from the rotating tip 32″. The coating canbe of any hard material that can be deposited in a thin layer. Such amaterial must have a tensile modulus which reasonably matches that ofthe tubing from which the guide wire is made if the coating is quitethick or flaking may occur when the wire is bent. Chromium plating (suchas that provided by Me92 Operations Inc. of Providence R.I.) allowsthicknesses of up to about 0.0008 inch to be applied to tubes of 0.010inch outside diameter and allows the tubing to be bent to radii of 0.375“or less without flaking of the coating.” Such coatings have hardnessesranging from 62 Rc-70 Rc, and have a modulus of about 33*10{circumflexover ( )}6 psi which is similar that of the steel tube. If a very thincoating is applied (e.g., less than 1 u) the coating has to be very hardto resist wear, but can have a bad mismatch in modulus and still allowthe tube to be bent to radii of 0.375 inch or less without flaking ofthe coating. A coating of titanium nitride about 2 u thick having ahardness of around 80 Rc functions well. Such a coating has a modulus ofaround 100*10{circumflex over ( )}6 psi and does not flake although muchstiffer than the steel tube at 28*10{circumflex over ( )}6 psi.

The guidewire 124′ is also advantageously made from more than onesegment of tubing as seen clearly in FIG. 19. The distal segment 124A′is made from a smaller tube than the proximal tube segment 124B′ and isfixedly secured thereto, e.g., welded, soldered or brazed, within theproximal tube 124B′. This arrangement allows the distal portion of theguide wire to navigate the tortuous coronary vasculature withoutexceeding the elastic limit of the steel tubing. A proximal segment of0.014 inch OD and 0.010 inch ID with a distal segment of 0.010 OD and0.005 ID both segments being of 304 S.S., ¾ hard tube gives the desiredflexibility.

It is not unusual for a guide wire to be coated with Teflon to providefor a low friction coefficient at the surface of the wire. In the caseof the present invention Teflon can be applied to the proximal sectionof the guide wire and the hard wear resistant coating can be applied tothe distal section. The combination provides for wear resistance at thedistal end and smooth torquing and pushability of the proximal portion.

Without further elaboration the foregoing will so fully illustrate ourinvention that others may, by applying current or future knowledge,adopt the same for use under various conditions of service.

What is claimed is:
 1. A tubular guide wire for use in a anintravascular system for opening a lumen in an occluded blood vesselportion of a living being's vascular system, the intravascular systemcomprising an instrument having a working head for opening the lumen inthe occluded blood vessel portion and being arranged to be guided to adesired position by said guide wire, said guide wire being arranged tobe bent during its deployment within the being's vascular system, saidguide wire including at least two tubular sections, one of said sectionsbeing a distal section and the other of said sections being a proximalsection, said distal section being located in a distal portion of saidguide wire and distally of said proximal section, said distal sectionhaving a proximal end portion, said proximal section having a distal endportion to which said proximal end portion of said distal section issecured, said distal section having a smaller outside diameter than saidproximal section, said distal section being arranged to accommodate theworking head of the instrument and being at least partially coated witha hard, wear resistant coating to prevent wear thereto by the operationof the instrument.
 2. The tubular guidewire of claim 1 wherein saidguidewire includes more than two of said tubular sections, with theoutside diameter of each tubular section being different than theothers.